Self-adjusting mechanical tappet



0a. 1 1963 w. HUMPHREYS 3,105,475

SELF-ADJUSTING MECHANICAL TAPPET Filed Nov. 14, 1961 INVENTOR. Jay/V M bWflPH/FZK? BY g M United States Patent Ofilicc 3,105,475 Patented Oct. 1, 1963 3,105,475 EELF-ADJUSTING EECHANIAL TAPEET John W. Hnmphreys, Muskegon, Mich, assignor to Johnson Products, Inc., Muskegon, Mich, a corporation of Michigan Fiied Nov. 14, 1961, Ser. No. 152,242 13 Ciaims. (Cl. 123--90) This invention relates to engine tappets and more particularly to self-adjusting mechanical tappets.

For years, a constant search has been made for effective, practical, dependable self-adjusting mechanical tappet structures. A few such structures have been devised, see for example patent application Serial No. 64,803, filed October 25, 1960, and assigned to the assignee herein. However, all of the mechanical self-adjusting tappets known to date are limited to an operating adjustment range of about 0.030 of an inch. Normal expansion and contraction of conventional overhead valve trains during engine operation is considerably less than this. Normal engine tolerances, however, cause valve train length variation of approximately 0.125 to 0.150 of an inch. Thus, known self-adjusting mechanical tappets have heretofore required additional manual adjustment means on the rocker arms. As a consequence, self-adjusting mechanical tappets have never been in a position to compete effectively with hydraulic tappets since they simply have not been capable of completely accommodating the normal valve train expansion and contraction.

The inventor herein, a veteran of many years in the field of tappets, has for the first time succeeded in developing a mechanical self-adjusting tappet capable of dependably adjusting conventionally sized tappets at least 0.180 inches. Such a tappet is therefore the chief object of this invention.

Another object of this invention is to provide a selfadjusting mechanical tappet capable of gradually and faithfully expanding or contracting with the gradual change in length of the valve train during engine heating or cooling. The adjusting components can be adapted to the smallest or the largest tappets known. The novel tappet is capable of operating under heavy valve spring loads. It is capable of operating with conventional oiling systems. its components possess excellent bearing surfaces causing long life to the tappet. The adjusting tappet components lock securely together at each adjusted position when the major spring load is applied to open the valve, thus acting as a nonslip compression unit.

These and many other objects will be apparent from a study of the following specification in conjunction with the drawings in which:

FIG. 1 is a side elevational sectional view of the novel tappet placed under major load; I

FIG. 2 is a sectional View showing the tappet in FIG. 1 with the major load removed;

FIG. 3 is a fragmentary, sectional view taken on plane IIIIII of FIG. 1;

FIG. 4 is a perspective view showing one form of the novel teeter bars; and

FIG. 5 is an enlarged fragmentary view of the elements in FIG. 1 showing the novel tappet at its maximum extended position and under major load.

Throughout this application, the term teeter is used to indicate an oscillating motion about a general fulcrum between the ends of the oscillating element. The fulcrum may exist because of any of several geometrical configurations underlying the oscillating member, including a gradual convex curvature. Thus the fulcrum may remain generally stationary or shift back and forth during oscillation.

Basically, the invention comprises a self-adjusting mechanical tappet utilizing a wedge and a pair of facing teeter bars. It includes a housing with the usual central bore, and having one open end and one closed end. Adjacent the closed end is a wedge element directed toward, and biased toward the open end. Adjacent the wedge surfaces which are arranged in a geometrically balanced pattern on the upstanding sides of the wedge, and in con tact therewith is a plurality of facing rocking shoes or teeter bars. These shoes are positioned divergently to ward the open end with respect to each other. Each has a curved inner edge at the end in con-tact with its respective wedge surface. Contacting each of the shoes or bars intermediate the ends along the back side thereof is a guide surface. The teeter bars rock or teeter on the surfaces over a fulcrum during operation and adjustment. The upper ends of the shoes contact a plunger which is movable axially in the housing to shift the push rod seat located thereon. The angle of each of the symmetrically positioned wedge surfaces is critical and is between 5 and 6 degrees approximately. The angle of each of the guide surface is critical and is at least two times that of the wedge angle. The fulcrum or rocking point along the back side of each teeter bar on the guide surfaces is preferably effected by providing both the shoe back and the adjacent guide surface with convex cylindrical surfaces normal to each other, or by providing the shoe back or the guide surface with a slightly spherical convex surface.

Referring to the drawings, in the form of the invention illustrated, the mechanical self-adjusting tappet 10 includes housing body 12 having one closed end .14 to provide a cam contacting surface, and an open end 16. P0- sitioned axially centrally in the enlarged bore 18 is wedge 26 adjacent end 14. The Wedge and its platform 22 may be integral, press-fitted together, or slip-fitted to gether as desired. Wedge 20 is biased toward open end 16 by a suitable spring 24 between platform 22 and end 14. Positioned adjacent the two opposite wedge surfaces 30 and 32 is a pair of guide surfaces 26 and 28 which may be part of an annular block means 34. The block may be press-fitted or slip-fitted into bore 18 against an aligning and retaining shoulder 38. Wedge surfaces 30 and 32 on the upstanding sides of the wedge are upwardly convergent with respect to each other toward open end 16. Guide surfaces 26 and 28 are upwardly divergent toward the open end 16 with respect to each other. Positioned between each of the wedge surfaces and the respective adjacent guide surfaces are mirror image rocking shoes or teeter bars 40 and 42. Each of these shoes contacts the respective wedge surfaces along the inner beveled, curved, lower edge 44 or 46. This curved contact facilitates the rocking movement to be explained hereinafter.

Each shoe contacts the guide surface 36 or 32 in a rocking or teetering manner intermediate the ends of the shoe, preferably on a one point contact. This contact may be effected by forming the individual shoes with a generally cylindrical convex back surface from top to bottom and forming the adjacent guide surface with a generally cylindrical convex curvature from side to side. The convex curvature of the shoe is shown in FIG. 1, with the convex curvature of the guide surface illustrated in FIG. 3. As an alternative, the back surface of the shoe or the guide surface may be provided with a generally spherical convex curvature, i.e. a hump 41 as illustrated in FIG. 4 on shoe 49. In contact with the slightly curved, convex upper ends of the shoes is a plunger element 50 including a push rod seat 52 for a typical push rod 54-, and retained by snap ring 62. If desired, a lubricant passageway 56 for lubrication of the mechanical tappet through the push rod 54 in a conventional manner may be supplied.

in order to cause the elements to flock together effectively when placed under the major (valve opening) load, and to adjust effectively by slippage therebetween without sticking when the major load is removed, it has been found that the wedge angle and the guide surface.

angle must be kept within critical limits. The two surfaces of the wedge should be at the same angle, somewhere between about 5 to 6 degrees with respect to the axis 60 of the tappet, bore 323, wedge 29. An angle of 6 degrees has been found to provide dependable operation over an extended period. The critical angle of the guide surfaces has been found to be about at least 2 times the wedge angle used. For example, with a wedge angle of 6 degrees, a guide surface angle should be 12 to 15 degrees. Here again bot-h guide surface angles should be the same.

Operation When the engine is in operation, the major load of the engine valve spring (not shown) is placed upon the push rod 54 to open the valve. The pressure applied by plunger 59 to the upper ends of shoes 49 and 42 causes them to heel in at the top and assume the position illustrated in FIG. 1 or that illustrated in FIG. 5 depending upon the curvatures involved, the valve spring load, the angles utilized, and the like. The point of contact between the shoes and the guide surface is then near or adjacent the lower end of the shoes. The components lock tightly together in this position. When the major load is removed withclosing of the valve, and only a minor load is applied to the tappet components by spring 24, shoes 49 and 42 rock or teeter simultaneously to the position shown in FIG. 2 with the bottom ends heeling in. The point of contact between the shoes and the contact surfaces is then adjacent or near the upper ends of the shoes. The bars teeter simultaneously in a coacting manner rather than alternately walking along the wedged surface as was characteristic of prior mechanical self-adjusters. The tendency of the shoes to assume different positions, depending upon whether or not the major load is applied, means that slight valve train clearance is stored up in the tappet when it is on the base circle of the cam shaft. The clearance, though only a few thousandths of an inch, is many times greater than the required tappet length adjustment for any one cycle. The tendency for the novel tappet to maintain a definite clearance results in operating tappet length adjustments to compensate for valve train length changes during engine operation. Extended experiments have shown that a tappet of conventional size using the novel combination will readily, repeatedly, .and dependably adjust to at least 180 thousandths of an inch. This tappet therefore provides all of the needed adjustment for valve trains in present engines. The potential is even greater with larger tappets. This novel self-adjusting tappet is therefore capable of being substituted for present hydraulic tappets. Moreover, the bearing surfaces of the elements provide long life, and the tappet is im'tially relatively inexpensive to manufacture.

Certain obvious modifications of the novel tappet may be apparent to those in the art upon studying this specification. This invention is therefore to be limited only by the scope of the appended claims and the reasonable equivalents thereto.

1 claim:

1. A self-adjusting mechanical tappet comprising: a housing body having an enlarged bore; said bore being open on its upper end; a plunger element slidably positioned in the open end of said bore and including an outer push rod seating surface; a wedge positioned axially centrally in said bore and having wedging surfaces on its upstanding sides; biasing means causing said wedge to be biased toward said open end; upwardly divergent guide surfaces positioned about said Wedge adjacent respective wedging surfaces on said wedge and spaced therefrom;

4 elongated rocking shoes having a first surface in contact with said wedging surfaces adjacent one end of said shoes; the surface of each of said shoes opposite said first surface making a rocking contact with its respective guide surface; and the upper end of each shoe being in contact with said plunger element.

2. A self-adjusting mechanical tappet comprising: a housing body having an enlarged bore; said bore being open on its upper end; a plunger element slidably positioned in the open end of said bore and including an outer push rod seating surface; a wedge positioned axia-lly centrally in said bore and having wedging surfaces on its upstanding sides; biasing means causing said wedge to be biased toward said open end; upwardly divergent guide surfaces positioned about said wedge adjacent respective wedging surfaces on said wedge and spaced therefrom; elongated rocking shoes having a first surface in I contact with said wedging surfaces adjacent one end of said shoes; the surface of each of said shoes opposite said first surface making a rocking contact with its respective guide surface; and the upper end of each shoe being in contact with said plunger element; each of said wedging surfaces being upwardly convergent at an angle of about 56 degrees to the axis of said wedge and bore.

3. A self-adjusting mechanical tappet comprising: a housing body having an enlarged bore; said bore being open on its upper end; a plunger element slidably positioned in the open end of said bore and including an outer push rod seating surface; a wedge positioned axially centrally in said bore and having wedgin'g surfaces on its upstanding sides; biasing means causing said wedge to be biased toward said open end; upwardly divergent guide surfaces positioned about said wedge adjacent respective wedging surfaces on said wedge and spaced therefrom; elongated rocking shoes having a first surface in contact with said wedging surfaces adjacent one end of said shoes; the sunface of each of said shoes opposite said first surface making a rocking cont-act with its respective guide surface; and the upper end of each shoe being in contact with said plunger element; each of said wedging surfaces being upwardly convergent at an angle of about 5-6 degrees to the axis of said wedge and bore; said guide surfaces being upwardly divergent with respect to each other at an angle of at least 2 times said wedge angle.

4. A self-adjusting mechanical tappet comprising: a housing body having a here; said bore being open on its uppe end; a plunger element slidably positioned in the open end of said bore and including an outer push rod seating surface; a wedge positioned axially centrally in said bore and having wedgin'g surfaces positioned in a geometrically balanced pattern on its upstanding sides; biasing means causing said wedge to be biased toward said open end; upwardly divergent guide surfaces positioned around said wedge adjacent said wedging surfaces on said wedge and spaced therefrom; elongated teeter bars, each havin the inner edge at the lower end thereof in contact with a wedging surface; the upper end of each bar being in contact with said plunger element; and the surface of each of said bars opposite said Wedge :being rockably in contact with one of said guide surfaces due to a convex curvature therebetween.

5. A self-adjusting mechanical tappet comprising: a housing body having a bore; said bore being open on its upper end; a plunge-r element slidably positioned in the open end of said bore and including an outer push rod seating surface; a wedge positioned axially centrally in said bore and having wedging surfaces positioned in a geometrically balanced pattern on its upstanding sides; biasing means causing said wedge to be biased toward said open end; upwardly divergent guide surfaces positioned around said wedge adjacent said Wedging surfaces on said wedge and spaced therefrom; elongated teeter bars, each having the inner edge at the lower end thereof in contact with a wedging surface; the upper end of each bar being in contact with said plunger element; and the surface of each of said bars opposite said wedge being rockably in contact with one of said guide surfaces due to a convex curvature there-between; said guide surface having a generally cylindrically convex curvature in one direction and said teeter bar back surface having a generally cylindrical convex curvature in a second direction substantially normal to the direction of said one direction.

6. The apparatus in claim 5 wherein said guide surface curvature is convex from side to side and wherein said bar surface opposite said wedge is convex from top to bottom.

7. A self-adjusting mechanical tappet comprising: a housing body having a bore; said bore being open on its upper end; a plunger element slidably positioned in the open end of said bore and including an outer push rod seating surface; a wedge positioned axially centrally in said bore and having wedgin' surfaces on the upstanding sides thereof; biasing means causing said wedge to be biased toward said open end; guide surfaces fixedly positioned around said wedge adjacent said wedging surfaces on said Wedge and being divergent with respect to each other toward said open end; elongated rocking shoes having a curved lower edge surface in contact with the wedging surfaces of said wedge; the upper end of each slice being in contact with said plunger element; said wedging surfaces being upwardly convergent at an angle of about 5-6 degrees to the axis of said wedge and bore; and the surface of each of said shoes opposite said wedge having at least a cylindrically convex curvature to obtain a rocking relationship on said guide surface.

8. A self-adjusting mechanical tappet comprising: a housing body having a bore; said bore being open on its upper end; a plunger element slidably positioned in the open end of said bore and including an outer push rod seating surface; a Wedge positioned axially centrally in said bore and having wedging surfaces on the upstanding sides thereof; biasing means causing said wedge to be biased toward said open end; guide surfaces fixedly positioned around said wedge adjacent said wedging surfaces on said wedge and being divergent with respect to each other toward said open end; elongated rocking shoes having a curved lower edge surface in contact with the wedging surfaces of said wedge; the upper end of each shoe being in contact with said plunger element; said wedging surfaces being upwardly convergent at an angle of about 5-6 degrees to the axis of said wedge and bore; the surface of each of said shoes opposite said wedge having at least a cylindrically convex curvature to obtain a rocking relationship on said guide surface; and said guide surface having a cylindrically convex curvature in a direction substantially normal to the direction of said shoe curvature.

9. A self-adjusting mechanical tappet comprising: a housing body having a bore; said bore being open on its upper end; a plunger element slidably positioned in the open end of said bore and including an outer push rod seating surface; a wedge positioned centrally in said bore and having symmetrically positioned wedging surfaces; biasing means causing said Wedge to be biased toward said open end; guide surfaces fixedly positioned on opposite sides of said wedge adjacent said *Wedging surfaces on said wedge and being upwardly divergent; elongated rocking shoes having a curved edge surface in contact with respective Wedging surfaces; said wedging surfaces being upwardly convergent at an angle of about 56 degrees to the axis of said wedge and bore; and the surface of each of said shoes opposite said wedge having a rocking relationship with its respective guide surface due to a spherically curved convex surface therebetween.

10. A self-adjusting mechanical tappet comprising: a housing body having a bore; said bore being open on its upper end; a plunger element slidably positioned in the open end of said bore and including an outer push rod seating surface; a Wedge positioned axially centrally in said bore and having symmetrically positioned wedging surfaces; biasing means causing said wedge to be biased toward said open end; guide surfaces fixedly positioned adjacent respective wedging surfaces on said Wedge and spaced therefrom; elongated teeter bars having a curved surface in contact with wedging surfaces of said wedge adjacent the lower ends thereof; each of said wedging surfaces being upwardly convergent at an angle of at least 2 times said wedge angle; and the surface of each of said shoes opposite said wedge having a rocking contact with its respective guide surface.

11. The apparatus in claim 10 wherein said rocking contact is effected by a generally cylindrical convex guide surface from side to side, and a generally cylindrical convex shoe back surface from top to bottom on said surface opposite said wedge.

12. The apparatus in claim 10 wherein said shoes and their respective guide surfaces have a convex hump therebetween.

13. A mechanical self-adjusting tappet comprising: a housing including an enlarged bore having an open end; a wedge positioned axially centrally in said bore; spring means biasing said wedge toward said open end; said wedge having symmetrically positioned wedge surfaces on the upstanding sides thereof convergent toward said open end, each at the same angle of about 5-6 degrees to the axis of said wedge and bore; coacting elongated rocking shoes, each having a curved end edge surface in contact with one of said wedging surfaces on said wedge; a fixed guide surface adjacent the surface of each of said rocking shoes opposite said wedge; said guide surfaces being divergent toward said open end with respect to each other at an angle of at least 2 times the angle of said wedge surfaces; said elongated rocking shoes rockably contacting said guide surfaces to enable rocking action of the shoes toward and away from each other; and an axially 'slidable plunger in contact with the ends of said rocking shoes opposite said curved edge ends, whereby said plunger may be shifted axially with coacting rocking action of said rocking shoes; and 'said plunger including a push rod seat.

References Cited in the file of this patent UNITED STATES PATENTS 1,806,099 Thomas May 19, 1931 2,615,439 Humphreys Oct. 28, 1952 2,672,132 Randol Mar. 16, 1954 

1. A SELF-ADJUSTING MECHANICAL TAPPET COMPRISING: A HOUSING BODY HAVING AN ENLARGED BORE; SAID BORE BEING OPEN ON ITS UPPER END; A PLUNGER ELEMENT SLIDABLY POSITIONED IN THE OPEN END OF SAID BORE AND INCLUDING AN OUTER PUSH ROD SEATING SURFACE; A WEDGE POSITIONED AXIALLY CENTRALLY IN SAID BORE AND HAVING WEDGING SURFACES ON ITS UPSTANDING SIDES; BIASING MEANS CAUSING SAID WEDGE TO BE BIASED TOWARD SAID OPEN END; UPWARDLY DIVERGENT GUIDE SURFACES POSITIONED ABOUT SAID WEDGE ADJACENT RESPECTIVE WEDGING SURFACES ON SAID WEDGE AND SPACED THEREFROM; ELONGATED ROCKING SHOES HAVING A FIRST SURFACE IN CONTACT WITH SAID WEDGING SURFACES ADJACENT ONE END OF SAID SHOES; THE SURFACE OF EACH OF SAID SHOES OPPOSITE SAID FIRST SURFACE MAKING A ROCKING CONTACT WITH ITS RESPECTIVE GUIDE SURFACE; AND THE UPPER END OF EACH SHOE BEING IN CONTACT WITH SAID PLUNGER ELEMENT. 